Struct rand::rngs::OsRng

pub struct OsRng;

A random number generator that retrieves randomness from from the operating system.

This is a zero-sized struct. It can be freely constructed with OsRng.

The implementation is provided by the getrandom crate. Refer to getrandom documentation for details.

Blocking and error handling

It is possible that when used during early boot the first call to OsRng will block until the system's RNG is initialised. It is also possible (though highly unlikely) for OsRng to fail on some platforms, most likely due to system mis-configuration.

After the first successful call, it is highly unlikely that failures or significant delays will occur (although performance should be expected to be much slower than a user-space PRNG).

Usage example

use rand::rngs::{StdRng, OsRng};
use rand::{RngCore, SeedableRng};

let mut key = [0u8; 16];
OsRng.fill_bytes(&mut key);
let random_u64 = OsRng.next_u64();
 
// OsRng is especially useful for seeding other RNGs (see also from_entropy)
let mut rng = StdRng::from_rng(OsRng).unwrap();
let _ = rng.next_u32();

Methods

impl OsRng

pub fn new() -> Result<OsRng, Error>

Deprecated since 0.7.0:

replace OsRng::new().unwrap() with just OsRng

Create a new OsRng.

Trait Implementations

impl Copy for OsRng

impl Default for OsRng

fn default() -> OsRng

Returns the "default value" for a type.

impl Clone for OsRng

fn clone(&self) -> OsRng

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for OsRng

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl RngCore for OsRng

fn next_u32(&mut self) -> u32

Return the next random u32.

fn next_u64(&mut self) -> u64

Return the next random u64.

fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data.

fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data.

impl CryptoRng for OsRng